Calcium-magnesium chloride and method of making same



CALCIUM MAGNESIUM CHLORIDE AND METHOD OF MAKING SAME Original Filed March 7, 1928 2 Sheets-Sheet 1 FEED [QR/NE: (P7 0 Ca C/ SOLUTION /N WHICH MOLECULAR RATIO OF LIES BETWEEN (o2 K N E M) 0.0 TO 2.00 1

l T WATER VAPOR OUT EVAPORATO/Q 50L uT/ Wm/m RESPECT r T0 TAcHYwarE=-C'aC@-2/'7 C-/H0 AND CQCI -ZH OQ 4 To 93C.

CRY ALS AND Mon/12 LIQUOR MOTHER LIQUOR SATURA TED SA ME A5 SOLUTION IN EVA PORATOR PRODUCT=CQCI AND l C/ 215 MECHANICAL MIXTURE 0F CRYSTALS 0F COG/ 411 6! IZ H 0 AND CQCI -ZH O IIYWH/CH RATIO or TOTAL M c/ g gg gg'yg IS SAME AS FEED BR/IYE TOTAL CQC/ MOTHER uauoe FEED BE/NE 7 CI CQC/ SOLUTION m WHICH MOLECULAR RATIO OF M11 LIES BETWEEN 2.00 AND 0.50 Cac/ l E FWVAPOR EflPO/EATOQ SATURA TED SOLUTION O TACHYDRITE (cQc/ z m c/ lzfl o) AND A NEW HYDRATED SALT, dz. ll cl -zCaC/ 611 0 393 T0 I52C CEY577-1L5 AND M0 THE/27ml U02 MOTHER L/auo PRODUCT Ca Cl AND 7 6/ AS A MECHANICAL MIXTURE 0F CRYSTALS OF 020/ OTALCQcI MOTHER L/ uoz INVENTORS 5 SAME/15 IIY FEED BR/NE.

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ATTORM m 5% MHWCH'I 9 w. R. COLLINGS ET AL 1,796,885

CALCIUM MAGNESIUM CHLORIDE AND METHOD OF MAKING SAME Original Filed March 7, 1928 2 Sheets-Sheet 2 FEED ale/NE (M 0 *QC/dsownom //v WHICH MOLECULAR KAT/0 OF L/E5 BETWEEN 0.50 AND ZERO 02 A P6125 Ca C/ BIZ/NE l WATER vAPb/z E VA POIQ A TOQ SOLUTION SATUIQATED WITH I2E5PECT T0. P7 -ZCaC/ 6 H 0 AND CaC/ .93 To APPROXIMATELY 1770.

CRYSTALS AND MOTHEE /GUOE MOTHER LIQUOJB 54 TURATEQ SAME AS SOLUTION //V EVA POBA To a CEY5TAL /NWH/CHEA7-/0 OF- TOTAL M c/l INCLUDING ADHER/IYG /5 AME A5 IN FEED BIG/IVE MOTHEQ F Fig. 3

ATTORNEYS .Original application filed March 7,

Patented Mar. 17, 1931 UNITED STATES PATENT OFFICE WILLIAM R. COLLINGS AND JOHN J. SHAFER, OF MIDLAND, MICHIGAN, ASSIGNORS TO I THE DOW CHEMICAL COMPANY, OF MIDLAND, MICHIGAN, A CORPORATION OF 7 MICHIGAN CALCIUM-MAGNESIUM CHLORIDE AND METHOD OF MAKING SAME application filed November-4, 1929. Serial No. 404,528.

The present improvements relate more particularly to a method of- .crystallizing from solutions saturated with hydrated metallic chlorides, and specifically chlorides of and one approved method for the recovery and separation from the residual brine of calcium chloride and magnesium chloride,

where thus found present in solution to gether,

is disclosed and claimed in U. S. Letters Patent No. 1,627,068 to A. K. Smith and C. F. Rrutton, dated May 3, 1927. However, in all such processes there. stillremains a residual mother liquor, that contains the chlorides in question in varying amounts.

One obj eot of the present improved process, accordingly, is to enable the working up of such'end liquor at any stage in the general process of treating brines of the type in question where the separation of the individual chlorides is discontinued, whether for com mercial or other reasons.

A further object is to obtain a product consisting of a mixture of such calcium and magnesium chlorides in the form of a free pouring,- non-caking, granular 'mechanical mixture of their hydrated chlorides in a wide range of ratios corresponding to that of the This nonend liquors utilized in the rocess.

-Hcaking, free pouring con ition is preferably No.'1,597,121 to P. Cottringer and W. R. Colobtained by superficially. drying such prod uet in accordance with U. S. Letters Patent lings, dated February 17 1925, but, if desired, further and standardizing the content of anhydrous chloess, limited thereto, the

at such percent- 75 per cent., 80

rides present in the product age as may be desired, e. g. per cent., etc. Accordingly, ratio of the two chlorides in the product may vary from time to time with a varying ratio thereof present in the available end l-iquor,. which constitutes the feed brine for the proc nevertheless the anhydrous content of the product may beheld at a constant figure for the purpose of yielding a standardized quality of mixed product.

To the accomplishment of the foregoing and related ends, the invention, then, consists of the steps and product hereinafter fully described and particularly pointed out. in the claims, the annexed drawing and the following description setting forth in detail several approved modes of carrying out the process and corresponding modifications in the product obtained, such disclosed modes and products, however, representing but several ofthe various ways in which the principle of the invention may be used.

In said annexed drawing Fig. 1 is a diagrammatic representation, somewhat on the order of a fiow sheet, showing in proper sequence the principal steps involved in carrying out one'form of our im- Mgcl (not by crystallization methods, whereby the calcium and magnesium chlorides are obtained as a mixture of hydrated chlorides in such proportion and composition that in the total analysis of the mixture and adhering mother liquor so obtained, the molecular ratio of 1928, Serial No..259,869, now Patent No. 1,738,492. Divided and this although the is the same as that in the feed brine, and the salts so obtained may be'thereupon dried'in; a current of hot gase without melting.

' a new compound talline mixture suitable Several hydrated chlorides and double I -mother liquor concentrations used. Thus some .of the hydrated chlorides which may be separated to obtain the above mentioned object are; magnesium chloride hexahydr'ate, MgOl fiH O;

tachydrite,

represented by the formula, MgGl .2OaCl .6H O; and calcium chloride dihydrate, binlng and proportioning the "above mentionedsalts, it is possible to obtain a mixture having anydesired molecular rati'oof When a calcium chloride-magnesium chloride brine of any analysis is fed to a salting out evaporator operating under any constant vacuum or pressure, water is removed and as a result a solid phase, or phases, will separate out of solution. If the said solid phase, or phases, be continuously removed by a filter and the mother liquor continuously returned to the evaporator withv the feed brine, the analysis of the mother liquor in the evap rator Will approach and a constant analysis. From this point on, the mother liquor analysis in the evaporator does not change substantially, the feed brine merely enters the evaporator, water is removed as vapor and the balance of the. feed is removed as a mixture of hydrated chlorides and ad hering mother liquor. This mixture may then be dried, as by hot air in a dryer, such as a dryer of the rotary kiln or shelf type, to obtain a dried, non-caking free flowing crysfor applying to' roads for dust prevention purposes, or other use.

In general, it is not important just what hydrates come out as the solid phase in the evaporator, when evaporating brine and returning the mother liquor separated from the crystals to the evaporator. The chief advantageous characteristics of the crystals, or crystahmixture, so obtained are; easy separation from the balling up. or the above reason, the salting out temperature in the evaporator is best kept low by maintaining a high vacuum on the evaporator so as to make the. crystal mix-' ture obtained most easilyseparable from the mother liquor.

The three figuresin the drawing, as stated, illustrate three difierent modifications of our method, or, more specifically, they show three specific ranges for feed brine composition CaCl 2I-I O. By variously comfinally approximate mothe'r liquor and capacity for drying b hot gases without melting or and evaporator temperature, for .each of which the particular hydrated end products thereby obtained are indicated.

Thus, assuming'abrine to contain Ca C1 MgCl NaCl, and H 0 in which the molecular ratio of I is less than 2 to 1, the preferred method of operation is illustrated in Fig. 1 and would be as follows Evaporate the brine under vacuum to a concentration of approximately {10 B. and separate the 40 B. liquor from the salt, which is practically insoluble in this strength liquor. The CaCI LMgCI liquor isthen fed to a salting evaporator, operating under-high mercury absolute pressure),

vacuum (say 1 in which water is removed as vapor and a thick crystal slurry of easy pumping consistpumped to a rotary suction filter which separates the "mother liquor quite completely from The crystals from the 'filter are handled as hereinafter described while the mother liquor is returned to the evaporator the'crystals.

.132 mole MgOl,

1.0 mole OaCl and 4.77 male H 0 1.0 mole Cat-31 and CaCl 2H O "and its saturated boiling point at 1 absolute pressure is approximate- This motherliquor is saturated with tachy ency is obtained. This slurry is then ly 70 C., the evaporator operdting'temfperature in-this case.

The first crystals obtained when starting up the process as described will not contain a molecular ratio of MgCl 081012 I equal to that in the feed liquor,unless the feed liquor happens to have the same MgCl, CaCL I s ratio as that of the equilibriummother liquor in the evaporator. Ho'wever, after the equilibrium mother liquor concentration has been attained the proportions of q GaOl 2H O, encigoaolzizuzo,

may be'zero and that the material being and adhering mother liquor coming off the rotary suctlon filter will be such as to give a .total analysis (.132 MgCl .CaCl .4.8H O),

the.

I Gael; ratio of which is identical with that of the feed. It is obvious that, if the OaCl, ratio in the feed liquor is nearly thefisame as that in the equilibrium mother liquor, the proportion of CaCl 2H O or of 2MgCl .CaC1 .12H O removed by the rotary suction filter will consist of one of the above named hydrates and the adhering mother liquor in such proportion as to give a total analysis of identical ratio with that of the feed liquor.

After equilibrium conditions have been attained they may be maintained as in customary manner by suitably controlling the heat in-put to the evaporator or the rate of feed or both.

The damp crystals obtained from the rotary suction filter are then dried preferably in a current of hot gases in a rotary dryer to dry up the adhering mother liquor and surface dry the crystals to give a free by the formula MgCl .2CaCl .6I-LO. These two hydrated crystalline. salts may be sepaconnection with the first method and the resulting product, as before, will contain the two chlorides in the same ratio as they are present in the feed brine.

Referring to the furthermodification in our method or process illustrated in Fig. 3,

the feed liquor here employed contains magnesium chloride and calcium chloride in a ratio lying between/13 and 0. Upon carrying out the evaporation of this liquor at a temperature. between 93 degrees and 177 degrees C., the solution in the evaporator becomes saturated with respect to the before mentioned new hydrated salt,

v and CaCl 2H O, so that crystals of these salts separate out and form a product in which the ratio of the total magnesium chloride to the total calcium chloride is the same as in the feed brine just as before.

For any composition' of feed liquor, there are one or more temperature ranges in which the above described process is operable for producing a product having the same MgCl 051L012 ratio as that of the feed. Thus in some cases a feed brine of a given analyses may be worked up-to a product of the same ratio by two different ways, that is by salting out two combinations of different hydrated, chlorides. These various possibili ties, together with one set of operating conditions suitable for working up any brine, are given in summary form in the following table which shows the general feed composition ranges, temperature ranges,

components of product, and specific temperature, pressure and equilibrium mother liquor composition therefor, for one mode of rated out in the same manner as described in working the process in all feed ranges, viz

Sample approximate operating Approx conditions operable range of Solid phases salting out i. 9. components molecular Operable temper- Approximate of product MgClz ature range Absolute equilibr um rat) 09.01; T m 1 pressure motherliquvr in feed to e 1 inches comp g g evaporator I 11g I 2 M185 .CaClz -2MgC1z.CaClz.12H;O plus CaClzJHzO pre- 2 2 70 c viously described. 1 to 1 'i 93 l 1.00

. I MgCl .2CaClz.6H 0 plus 2MgClz.C8.Clz. 1 HHiQ I 1 1 to 1 Above.93C. 120C. 10" 1 L00 .5 0 O .038 MgClz.2CaClz.6H2O plus C6-Clz.2HzO. T to Above 93 C. 130 C.- 12 n It may be observed that while according to the process of U. S. Patent 1,627,068 crystalline double salts of magnesium and calcium are produced for the purpose of increasing the, ratio of the magnesium to calcium therein, and magnesium chloride, or calcium chloride, is finally separated therefrom as a single chloride, we produce mix? tures of diflerent double salts or mixtures of different hydrated salts, and then convert those into dried granular or crystalline prod- .ucts' containing the mixed chlorides of magnesium and calcium in any desired ratio, e. g., in that ratio in which they may exist or may be available in the brine or mother liquor source.

From the foregoing exemplifications of the process, it will accordingly be seen that the latter enables the working up of brine ranging from a pure calcium chloride brine to one in which the ratio of magnesium'chlo ular product having very desirable proper ties. In short, our new process'admirably solves the question of how to utilize and work up advantageously the mother liquors remaining from the production of pure mag-- nesium chloride and/or pure calcium chloride, or both, from brines or liquors in which such chlorides are present in solution together. The recovery or separation of these pure salts may be carried out to any desired extent Without regard to the ratio in which they are left present in the residual solution or mother liquor since the latter by'means of the present process may be converted into the form of the mixed .granular hydrated single or double chlorides, or both, as hereinbefore set forth. 7

The aforesaid hydrated salt mixtures we have found more easily separated by filtration or draining at all temperature ranges'in the first method (Fig. 1) 'and at the lower temperature ranges-1n the second method (Fig. 2). Indeed they may be even centrifuged without the drawback of caking to a solid mass and they'may be readily separated upon arotary suction filter in a continuous .manner corresponding with the approximate rate .in which the salts are formed in the evaporator. The process, accordingly, lends itself admirably for continuous operation,

' employing an evaporator under reducedv pressure and temperature control with continuous feed, continuous withdrawal of mother liquid and crystals, continuous separation on a filter with production of a continuous stream of productin moist, granular form and a like continuous stream of mother liquor for return to the evaporator. Moreover, the crystalline product thus separated may, if desired, be dried in a continuous drier.

This application is a division of our Patent 1,7 38,492, application filed March 7, 1928. Other forms of applying the principle of our invention may be employed instead of the ones here explained, change being made in the method or composition, provided the steps or ingredients stated by any of the following claims or the equivalent of such stated steps or ingredients be employed.

We therefore particularly point out and distinctly claim as our ihvention:'

1. In a method of making a product of the character described, the steps which consist in adding a solution containing a mixture of calcium and magnesium chlorides to a mother liquor saturated with respect to tachydrite and calcium chloride dihydrate, the molecular ratio of magnesium chlorideto calcium chloride in such added than 2.00, and simultaneously evaporating solution being less such mother liquor to maintain thesamc approximately at such point of saturation.

2. In a method of making a product of the character described, the steps which consist in adding a solution containing a mixture of calcium and magnesium chlorides to a mother liquor saturated with respect to tachydrite and calcium chloridedihydrate, the molecular ratio of magnesium chloride to calcium chloride in such added solution being less than 2.00, and simultaneously evaporating such mother liquor at a temperature between 45? and 93 (1., whereby such mother liquor is maintained approximately at such point of satur tion.

' 3. n a method of making a product of the character described, the steps which consist in adding a solution containing a mixture of calcium and magnesium-chlorides to a mother liquor saturated with respect to tachydrite and calcium chloride dihydrate, the molecular ratio of magnesium chloride to calcium chloride in such added solution lying between 0. and 2.00, and simultaneously evaporating" such mothor liquor to maintain the same approximately at such point of saturation. I

4. As a new article ofmanufacture, a free flowing, non-caking mixture of hydrated crystal chlorides of magnesium and calcium precipitated as crystals of tachydrite and calcium chloride dihydrate from a solution saturated with respect to su'chchlorides, such crystals being superficially dehydrated to the point where their tendency to cake together in the package is reduced.

Signed by us this 31st day of October, 1929.

WILLIAM R. COLLINGS. JOHN J. SHAFER. 

